A series of novel chiral azodye homo- and copolymers has been investigated for applications in optical data processing and display technology. Supramolecular chirality in those systems due to
helical superstructure leads to specific photo-optical response to circularly polarized light and, therefore, for creation of advanced photorecording media, especially for polarization holography.
Highly twisted smectic-like mesophases of side chain homo- and copolymers (short pitch TGB A* phase) appear visually transparent and optically isotropic but possess a hidden liquid crystalline
ordering, giving rise to rewriteable photorecording in relatively thick polymer films with high photoinduced phase retardation and diffraction efficiency. The amplitude gratings were written in polymer films with linearly polarized light but the phase gratings with circularly polarized light. Evolution of the photoinduced birefringence and diffraction efficiency, η<sub>1</sub>, is studied. For some polymers, polarization gratings are obtained with η<sub>1</sub> value above 30%; overmodulation effects of the grating recording are observed and discussed. The effect of dark self-amplification is reported.
The polymer P8*5 has a frustrated phase behaviour. It shows either the sequence of mesophases g 3 1-35°C S 44°C SA* 47°C i or g 3 1-35°C TGBC 47°C i. It is not completely understood yet under which conditions one of the phase sequences is prefered. Both phase sequences are kinetically stable and reproducible. Similar behaviour has been observed earlier1'2 for the acrylic copolymer C37, but no detailed study ofthe two phase modification was carried out. The "subcritical" phase condition of the substance should be the reason for extremely low driving voltage values of optical switching in S* p1c ( O.2V4tm) and for extremely low untwisting voltages (0.5 - 1.5V/iim), as well as for the low clearing point values and for the existence of the switchable Sc p close to room temperature. The siloxane main chain of the polymer should be less preferable for the formation of a highly twisted, weakly birefringent TGB-like phases, as compared with the methacrylic one, since for the latter such a frustration can be achieved only by addition of63% of nonchiral moieties to the structure ofthe copolymer"2. Keywords: ferroelectnc polymer liquid crystal, tilt angle, pyroelectric coefficient, hysteresis, X-ray